202
FXUS61 KCTP 050356
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1056 PM EST Wed Dec 4 2024

.SYNOPSIS...
* Widespread snow showers, localized snow squalls, and strong
  winds 40-50 mph will likely result in hazardous travel impacts
  late tonight into Thursday
* Lake effect and upslope snow continues into late week with
  significant storm total accumulations probable in the favored
  snowbelts and higher ridgetop elevations
* Colder than average temperatures and breezy conditions
  continue through the end of the week followed by a warming
  trend over the weekend into early next week

&&

.NEAR TERM /THROUGH THURSDAY/...
Radar loop at 03Z shows light to occasionally moderate snow
falling across roughly the northern half of PA in region of warm
advection at the nose of a 55kt low level jet. Latest model
guidance indicates the focus of overrunning snow will remain
over Northern PA through 06Z. Latest model qpf suggests up to an
additional inch of accumulation is likely between 03Z-06Z where
a southerly flow is forced to ascend the higher terrain north
of I-80.

WAA/synoptic scale snow transitions to frontal snow showers and
squalls associated with a sharp arctic frontal passage btwn
roughly 06-13Z Thu. Deep 500-700mb height anomalies and strong
synoptic-scale forcing will provide sufficient lift, along with
ample 850-700mb FGEN and some progged surface-based CAPE to
foster a line of snow showers and some intense squalls with the
fropa early Thursday morning. Boundary layer temperatures are
more questionable along and to the southeast of I81/78 corridor,
but fast moving squalls producing brief bursts of snow (or
quick rain to snow transition) should occur in parts of the
Lower Susquehanna Valley closer to the morning peak commute.
Remember there are no safe places on a highway during a snow
squall, as visibility drops significantly and roads can become
snow covered quickly, making it hard to see on the road and slow
down when necessary.

A dry slot behind the exiting cold front should result in
breaking clouds downwind (east) of the Alleghenies Thursday
morning. The focus Thursday then shifts to strong/gusty winds
and a developing lake effect and upslope snow regime. Subsidence
forced by differential anticyclonic vorticity advection and the
passage of a strong isallobaric couplet point to the development
of strong winds behind the exiting cold front Thursday morning,
which should persist through the day. Latest Bufkit soundings
support gusts in the 40-50kt range beginning over the western
part of the forecast area before dawn and maybe just after dawn
in the east.

CAMs indicate steady, mostly light lake-enhanced orographic snow
over the NW Mtns will transition to a more focused single
band emanating from Lake Huron by late in the day. These band
will not only bring heavy snow to the recently hard hit areas in
the northwest mtns, but potentially extend farther to the
southeast into central PA by Thu evening. Strong orographic
lift will support upslope snow over the Laurel Highlands with
near blizzard conditions possible on the ridgetops.

There will only minor tweaks to storm total snowfall maps with
max accums 6-15" in the NW mtns, 4-8" along the Laurel Highlands
and a coating up to 2 inches elsewhere. Snow character should
be dry/fluffy variety where heavy snow accums are expected.
Strong blustery winds may result in significant blowing and
drifting snow. Model time height sections indicate most of the
lift occurring within the DGZ, pointing toward high snow/water
ratios. However, settling caused the gusty winds may keep ratios
below 20/1.

Highs Thursday will be 10 to 20 degrees below the historical
average, ranging from the low 20s over the Laurel Highlands to
mid 30s in parts of the mid/lower Susq Valley. CAA may result in
neutral to slowly falling temps during the daylight hours of
Thursday. It will feel much colder with wind chills in the
+single digits and teens.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
Lake effect and upslope snows continue through late week with
snow piling up in the favored snowbelts. Friday looks like the
coldest for max temps remaining at or below the freezing mark
across the majority of the CWA (10-20F below climo).

Sfc-850mb ridge axis crosses the state Friday night which should
spell and end to the lake effect as trajectories shift/back to
the WSW focusing lingering lake effect snow showers/bands into
southwest NY state. Temps slowly begin to moderate on Saturday
with daytime highs trending +2-6F warmer day/day.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Strong backing of the LLVL flow to the SSW Saturday night
through Sunday will quickly put an end to any lingering,
light lake effect snow showers as the Dendritic Growth
Zone shifts above 12,000 FT AGL and into the warm advection
generated, mid-cloud layer with a 5000-7000 ft thick layer of
dry air beneath it.

Upper level ridging and a surface high passing off of the East
Coast should translate to fair and significantly milder weather
Sunday, as the return southwest flow develops. GEFS 2m temp
anomalies suggest highs Sunday will be several degrees above
average, ranging from around 40F over the N Mtns, to around 50F
in the southern valleys. However, a fairly gusty swrly wind of
10-20kts will keep a chill in air with apparent temps still in
the 30s north and west, to low and mid 40s in the SE.

The bulk of medium range guidance supports a period of rain
Monday associated with warm advection ahead of a weakening
shortwave lifting into the Eastern Grt Lks. Can`t completely
rule out an initial wintry mix over the higher terrain of
Northern PA Monday AM, but lack of a blocking high and current
progged thermal fields point toward all rain. The low level jet
and plume of highest pwats should shift east of the region by
Monday night, causing rain to taper off. Ensemble plumes
currently indicate most likely rain totals by late Monday of
0.25 to 0.50 inches. Warm advection ahead of an approaching warm
front could support lingering low clouds and spotty showers
Monday night.

Latest EPS/GEFS both track a cold front across Central PA
Tuesday, which is likely to be accompanied by scattered rain
showers. Temperatures could potentially spike well into the 50s Tuesday,
if the region breaks into the warm sector ahead of the
approaching front. A trend toward drier and cooler conditions is
expected behind the front next Wednesday. However, an upstream
mid level trough and potential secondary cold front will keep
the chance of a few rain showers in the forecast for midweek,
with rain/snow showers possible over the Alleghenies.

&&

.AVIATION /04Z THURSDAY THROUGH MONDAY/...
Light snow and IFR conditions continue across most of the area
this evening as a brief shot of warm advection moves across the
state. This will be followed overnight by a cold frontal
boundary.

As the colder air returns across Lake Erie, expect widespread
snow and squalls across the northern half of the state and
higher elevations of the Laurel mountains. This will impact KBFD
and KJST with occasional IFR to LIFR through the forecast
period. To a lesser extent, KAOO and KUNV will drop to MVFR at
times being further from the lake.

We are still expecting a 6-10 hour period of LLWS late
today/tonight at all terminals until the front passes and we see
a widespread increase in surface gusts.

Behind the cold front a reinforcing shot of cold air along with
blustery W/NW winds are expected for Thursday. Sustained NW
winds around 15 to 25 kt and gusts of 40-45 kts expected.

Outlook...

Fri-Sat...IFR/MVFR most likely at KBFD and possible at KJST in
scattered lake effect and upslope snow showers. MVFR to low VFR
expected elsewhere. Decreasing W/NW winds.

Sun...Becoming VFR, with a light southerly breeze developing.

Mon...The pattern warms and the threat for rain increases.
Periods of restrictions are possible in the rain...due to low
clouds and fog.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Lake Effect Snow Warning until 8 PM EST Friday for PAZ004>006-
010-011.
Wind Advisory until 7 PM EST Thursday for PAZ004>006-010>012-
017>019-024>028-033>037-041-042-045-046-049>053-056>059-
063>066.
Winter Weather Advisory until 1 PM EST Friday for PAZ012-018.
Winter Storm Warning until 1 PM EST Friday for PAZ017-024-033.
Winter Weather Advisory until 10 AM EST Thursday for PAZ037-
041-042.

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Fitzgerald/Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Lambert/Fitzgerald
AVIATION...Lambert/Tyburski